bearing question - has me scratching my head

E

ecdez

Forum Guest
Register Today
OK, so I pulled the bearing out of a drill press (http://www.hobby-machinist.com/threads/help-id-this-drill-press.58476/#post-481498) because they need some attention. One needs replaced so I looked up the part number "3203" and find that they should be 40mm o.d. x 17mm bore x 12mm wide. No problem, plenty out there. The problem is all my measurements match on the one I have except the inner bore. Mine measure .665" or 16.89 mm; close, but not quite there. I have no experience with bearing replacement. Is this normal? Should I just buy one and try it or am I way off here?

As a side question, the drill has small oil ports above each bearing suggesting the originals had to be oiled. The ones I removed have a seal on the bottom but not the top. It looks like the seals were removed on the top of each bearing. Should I just get sealed ones and get over it or put it back like it was?
 
In my experience, bearings tend to be made with nice round numbers, either metric or imperial, for dimensions. How did you measure the I.D.? Measurements of small bores with calipers can read low if not careful. A more accurate way would be to measure the shaft diameter.

I would just get sealed bearings and forget about lubing them.
 
I did use calipers! Didn't think about the id throwing it off. I was wondering about the rounding too. I was going to measure the shaft but it's all the way outside :grin:. I will double check the shaft later; it's impossible to walk in my shop without getting dirty.
 
I would just get a 3203-2RS bearing made by a known and trusted manufacturer (Koyo, SKF, NSK, etc). If it were me I would get a "premium" grade (all bearings are not the same grade - tolerance) and not remove the top seal unless the machine was going to be in constant use. The lubrication in a modern sealed bearing should last for many years in a home or small shop. However, you can remove the top seal with a pick if you want to restore to original.
 
3203-2RS was one of the options I was looking at on Grainger. "restore to original" is out the window since the vari-drive setup is missing. No worries about that though. The deal on the machine was right!
 
Don't remove the seal!!!! Leave it as is. You pull the seal and drip oil into the bearing, you containment the bearing grease and can cause failure within the bearing. The oil will cause separation of the clays and other ingredients of the grease, which some of those elements can cause bearing failure since they do not provide any lubrication abilities. Just don't do it. If you insist in doing so remove both seals, that way the oil over time will replace all of the grease with oil. And of course,, it will drip out the bottom onto whatever you are working on.
I have run into situations where the bearing manufacture will make this bearing in more than one bore size and width. I have a lathe that uses this same bearing series as a front spindle bearing. And someone replaced it with a 5500 series shielded bearing. The bearing is damaged from both the wrong one installed and headstock oil contaminating the factory grease in the bearing. The 3000 series bearing with most manufactures is a high angular contact double row bearing. Generally supplied as a class ABEC 1, general purpose bearing. For a drill press, should be just fine. For a spindle bearing for a lathe, well, it'll work, probably never be notice of any inaccuracy in machining. But for me to find a class 5 bearing which the lathe had when it left the factory, untainable today! A class 3 bearing I can have at around $400 if I choose to do so. In a 3203 bearing, a person should be able to find one in a class 3 for under $100 if you really see a need for it in a drill press. Ken
 
OK, so I pulled the bearing out of a drill press (http://www.hobby-machinist.com/threads/help-id-this-drill-press.58476/#post-481498) because they need some attention. One needs replaced so I looked up the part number "3203" and find that they should be 40mm o.d. x 17mm bore x 12mm wide. No problem, plenty out there. The problem is all my measurements match on the one I have except the inner bore. Mine measure .665" or 16.89 mm; close, but not quite there. I have no experience with bearing replacement. Is this normal? Should I just buy one and try it or am I way off here?

As a side question, the drill has small oil ports above each bearing suggesting the originals had to be oiled. The ones I removed have a seal on the bottom but not the top. It looks like the seals were removed on the top of each bearing. Should I just get sealed ones and get over it or put it back like it was?

A 7203 is 40 x 17 x 12, single row, angular contact (it matters which way you install it). A 3203 is 40 x 17 x 17.5, double row (doesn't matter which way you install it).

Lots of options available:

https://www.mcmaster.com/#standard-ball-bearings/=17eysay
 
Thanks guys! One of the things I like most about this forum is that no matter how obscure I think the topic might be (not that this one's that odd) there's always someone here who's delt with it or has worked in that field or something and freely shares their knowledge and experience.

By the way, I mic'ed the shaft yesterday and it's 0.669" or 16.992mm. Seems just right for a slight press fit.
 
Bearings might have numbers on them, but You cannot tell when the MFG ordered a special size. Have a friend that sold bearings commercially for years, He said He had seen about 5 sizes for a 6202 bearing. I had one marked lie that. Best to always measure them or take them With You if going to the store.
 
Back
Top